1. Field of the Invention
The present invention relates to a liquid crystal display device (LCD), and more particularly, to an LCD that can be manufactured by a simplified process and a method of manufacturing the same.
2. Description of the Related Art
A liquid crystal display device (LCD) is considered as the next generation display device because it has good portability and low power consumption and is also technology-intensive and high value-added.
The LCD includes a liquid crystal panel having two glass (or plastic) substrates between which liquid crystal is filled. A transparent electrode (e.g., common electrode and pixel electrode) is formed on each of the substrates to apply a given voltage to the filled liquid crystal. The light transmittance of the liquid crystal panel is controlled by a voltage applied to the transparent electrode, and characters/images are displayed by a light shutter effect.
An active matrix type LCD including a switching device for driving each pixel is most widely used because of its excellent resolution and performance in displaying a moving image.
In general, a method of manufacturing the liquid crystal panel includes an array substrate fabrication process for forming switching devices and pixel electrodes, a color filter substrate fabrication process for forming a color filer and a common electrode, and a liquid crystal cell process for interposing liquid crystal between the two substrates.
When compared to the array substrate fabrication process and the color filter substrate fabrication process, the liquid crystal cell process requires few or no repeated operations. The liquid crystal cell process can be broadly divided into an alignment layer forming operation for alignment of liquid crystal molecules, a cell gap forming operation, a cell cutting operation, and a liquid crystal injecting operation.
FIG. 1 is a sectional view of a related art LCD.
Referring to FIG. 1, the LCD includes an array substrate 30 and a color filter substrate 10 that are spaced apart from each other by a predetermined distance, and a liquid crystal layer 50 interposed between the array substrate 30 and the color filter substrate 10.
The array substrate 30 includes a transparent substrate 1, a gate electrode 32 formed on the transparent substrate 1, a gate insulation layer 34 formed on the transparent substrate 1 including the gate electrode 32, a semiconductor layer 36 including an active layer 36a and an ohmic contact layer 36b sequentially formed on the gate insulation layer 34 corresponding to the gate electrode 32, and source/drain electrodes 38 and 40 formed on the semiconductor layer 36 and spaced apart from each other by a predetermined distance. The gate electrode 32, the semiconductor layer 36, and source/drain electrodes 38 and 40 constitute a thin film transistor (TFT) T.
Although not illustrated in FIG. 1, a gate line connected to the gate electrode 32 is formed in a first direction, and a data line connected to the source electrode 38 is formed in a second direction crossing the first direction. A region where the gate and data lines cross each other is defined as a pixel region P.
A passivation layer 42 with a drain contact hole 44 is formed on the TFT T, and a pixel electrode 48 electrically connected to the drain electrode 40 by the drain contact hole 44 is formed in the pixel region P.
The color filter substrate 10 includes a transparent substrate 5, a color filter layer 14 formed on the transparent substrate 5 at a position corresponding to the pixel electrode 48 to transmit light of a specific wavelength, and a black matrix 12 formed at an interface between the transparent substrate 5 and the color filter layer 14 to block light leakage and light flow into the TFT T.
A common electrode 16 for applying a voltage to the liquid crystal layer 50 is formed on the color filter layer 14 and the black matrix 12.
For prevention of leakage of the liquid crystal layer 50, the edges of the array substrate 30 and the color filter layer 10 are sealed with a seal pattern 52.
A ball spacer 54 is disposed at a predetermined region between the array substrate 30 and the color filter substrate 10 to maintain a cell gap therebetween.
The ball spacer 54 is formed of organic material or glass fiber with elasticity against an external pressure. The ball spacers 54 are randomly dispersed on the substrates 10 and 30, and thus have the following problems.
First, the possible movement of the ball spacers may cause defects in the alignment layer.
Secondly, the absorptive power between the ball spacer and a neighboring liquid crystal molecules may cause light leakage around the ball spacer.
Thirdly, in a case of a wide-screen LCD, it is difficult to maintain a stable cell gap.
Fourthly, the ball spacer is elastic and movable and thus may case a ripple phenomenon when a screen is touched.
Consequently, it is difficult to obtain a high quality image in the LCD whose cell gap is maintained using the ball spacers.
To solve these problems, there is proposed a method of forming a spacer pattern (i.e., a patterned spacer) at a predetermined position by photolithography.
The patterned spacer is fixed to a non-pixel region of the LCD. Therefore, the use of the patterned spacer makes it possible to easily maintain the cell gap, prevent the light leakage, precisely control the cell gap for an LCD requiring a small cell gap, enhance the solidity of the LCD, and prevent the ripple phenomenon from occurring when the screen is touched.
FIG. 2 is a sectional view of a related art LCD including patterned spacers.
Referring to FIG. 2, the LCD includes an array substrate 70 and a color filter substrate 60 that are disposed to face each other. A TFT T and a pixel electrode 72 of transparent conductive material connected to the TFT T are formed on the array substrate 70. A black matrix 62 is formed on the color filter substrate 60 at a position corresponding to the TFT T, a color filter 64 is formed on the black matrix 62 at a position corresponding to the pixel electrode 72, and a common electrode 66 is formed on the color filter 64.
A patterned spacer 74 is formed between the black matrix 62 and the TFT T to maintain a uniform cell gap between the array substrate 70 and the color filter substrate 60.
A liquid crystal layer 80 is interposed between the array substrate 70 and the color filter substrate 60.
In the related art, the patterned spacer is formed on one of the substrates 70 and 60 and then the substrates 70 and 60 are attached together, thereby maintaining a uniform cell gap between the substrate 70 and 60.
However, the patterned spacer 74 must be formed by a separate mask process. This causes an increase in the complexity and cost of the entire manufacturing process.